Question

我正在vb.net中创建一个程序，并想知道是否有一种方法可以使用一个按钮执行多个查询而无需添加第二个按钮。

就像我有两个文本框，一个是日期，另一个是名称。我想要做的是，如果我点击搜索，日期和名称框都填写，我希望它根据该日期搜索名称。但如果只填写名称，我想搜索该名称下的所有内容。

这就是我所拥有的。现在它只进行一次搜索：

Private Sub cmdSearch_Click(sender As System.Object, e As System.EventArgs) Handles cmdSearch.Click
        Dim conn As New MySqlConnection
        Dim myCommand As New MySqlCommand
        Dim myAdapter As New MySqlDataAdapter
        Dim myData As New DataTable
        Dim SQL As String
            SQL = "SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name " _
        & ", start.timestamp `Time In` " _
        & ", end.timestamp `Time Out` " _
        & ", timediff(end.timestamp, start.timestamp) Duration " _
     & "FROM user u " _
        & ", user_group ug " _
        & ", ( " _
           & "select * " _
              & ", ( " _
                 & "select event_id " _
                 & "from event L2 " _
                 & "where L2.timestamp > L1.timestamp " _
                    & "and L2.user_bannerid = ?bannerID " _
                     & "and L1.user_bannerid = ?bannerID " _
                 & "order by timestamp limit 1 " _
                & ") stop_id " _
           & "From event L1 " _
          & ") start " _
     & "join event end on end.event_id = start.stop_id " _
     & "where start.status = 'In' " _
        & "and end.status='Out' " _
        & "and u.user_bannerid = ?bannerID " _
        & "and start.user_bannerid = ?bannerID " _
        & "and ug.user_bannerid = ?bannerID " _
        & "and ug.group_id = ?GroupID " _
        & " and start.group_id = ?GroupID " _
     & "UNION " _
     & "SELECT null, null, null, CAST(sum(duration) as Time) " _
     & "FROM " _
     & "( " _
        & "SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name " _
           & ", start.timestamp `Time In` " _
           & ", end.timestamp `Time Out` " _
           & ", timediff(end.timestamp, start.timestamp) duration " _
        & "from user u " _
           & ", user_group ug " _
           & ", ( " _
              & "select * " _
              & ", ( " _
                 & "select event_id " _
                 & "from event L2 " _
                 & "where L2.timestamp > L1.timestamp " _
                    & "and L2.user_bannerid = L1.user_bannerid " _
                 & "order by timestamp " _
                 & "limit 1 " _
                & ") stop_id " _
              & "from event L1 " _
             & ") start " _
        & "join event end on end.event_id = start.stop_id " _
        & "where start.status = 'In' " _
           & "and end.status = 'Out' " _
           & "and u.user_bannerid = ?bannerID " _
        & "and start.user_bannerid = ?bannerID " _
        & "and ug.user_bannerid = ?bannerID " _
        & "and ug.group_id = ?GroupID " _
        & " and start.group_id = ?GroupID " _
     & ") total "
            conn.ConnectionString = myConnString

            Try
                conn.Open()

                Try
                    myCommand.Connection = conn
                    myCommand.CommandText = SQL
                    myCommand.Parameters.Add("?bannerID", txtBannerID.Text)
                    myCommand.Parameters.Add("?GroupID", cboGroups.SelectedValue)

                    myAdapter.SelectCommand = myCommand
                    myAdapter.Fill(myData)

                    dgvStatus.DataSource = myData
                    dgvStatus.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill
                Catch myerror As MySqlException
                    MsgBox("There was an error reading from the database: " & myerror.Message)
                End Try
            Catch myerror As MySqlException
                MessageBox.Show("Error connecting to the database: " & myerror.Message)
            Finally
                If conn.State <> ConnectionState.Closed Then conn.Close()
            End Try

        End Sub

Answer 1

您可以通过单击按钮时检查文本框来执行此操作。复杂的查询可能很难直接使用，但它归结为构建您想要的命令字符串:(简化方式）

查询字符串构建：

    Dim SQL As String = "SELECT SomeFields FROM TableWhatever WHERE Date=?Date"
    If txtName.Text.Trim <> "" Then
        SQL &= " Name=?Name"
    End If

如果在where子句

中添加参数

    ... Connection stuff here

    myCommand.CommandText = SQL
    If txtname.text.Trim <> "" Then
        myCommand.Parameters.Add("?Name", txtName.Text.Trim)
    End If

vb.net搜索按钮多个查询

1 个答案: